On Wed, 2015-07-22 at 10:54 -0600, Alex Williamson wrote: > On Tue, 2015-07-21 at 19:44 +0200, Gerald Schaefer wrote: > > When a user completes the VFIO_SET_IOMMU ioctl and the vfio-pci device is > > removed thereafter (before any other ioctl like VFIO_GROUP_GET_DEVICE_FD), > > then the detach_dev callback of the underlying IOMMU API is never called. > > > > This patch adds a call to vfio_group_try_dissolve_container() to the remove > > path, which will trigger the missing detach_dev callback in this scenario. > > > > Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> > > --- > > drivers/vfio/vfio.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > > index 2fb29df..9c5c784 100644 > > --- a/drivers/vfio/vfio.c > > +++ b/drivers/vfio/vfio.c > > @@ -711,6 +711,8 @@ static bool vfio_dev_present(struct vfio_group *group, struct device *dev) > > return true; > > } > > > > +static void vfio_group_try_dissolve_container(struct vfio_group *group); > > + > > /* > > * Decrement the device reference count and wait for the device to be > > * removed. Open file descriptors for the device... */ > > @@ -785,6 +787,7 @@ void *vfio_del_group_dev(struct device *dev) > > } > > } while (ret <= 0); > > > > + vfio_group_try_dissolve_container(group); > > vfio_group_put(group); > > > > return device_data; > > > This won't work, vfio_group_try_dissolve_container() decrements > container_users, which an unused device is not. Imagine if we had more > than one device in the iommu group, one device is removed and the > container is dissolved despite the user holding a reference and other > viable devices remaining. Additionally, from an isolation perspective, > an unbind from vfio-pci should not pull the device out of the iommu > domain, it's part of the domain because it's not isolated and that > continues even after unbind. > > I think what you want to do is detach a device from the iommu domain > only when it's being removed from iommu group, such as through > iommu_group_remove_device(). We already have a bit of an asymmetry > there as iommu_group_add_device() will add devices to the currently > active iommu domain for the group, but iommu_group_remove_device() does > not appear to do the reverse. Thanks, BTW, VT-d on x86 avoids a leak using its own notifier_block, drivers/iommu/intel-iommu.c:device_notifier() catches BUS_NOTIFY_REMOVED_DEVICE and removes the device from the domain (the domain_exit() there is only used for non-IOMMU-API domains). It's possible that's the only IOMMU driver that avoids a leak due to the scenario you describe. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
